The present invention relates to a boiler with horizontal boiler sections consisting of several horizontal heat exchanger elements for transferring the heat from the heating medium to the heat carrier medium, wherein at least the inner heat exchanger elements consist of pipes carrying the heat carrier medium which are provided with exterior convection fins.
In a known boiler of this type the boiler sections consist of a frame conducting the heat carrier medium, i.e. the frame contains an inner surrounding liquid channel, wherein depending on the size of the boiler a number of pipes are secured in the frame as additional heat exchanger elements and are in flow communication with the frame channel. The vertical channel connection of the boiler sections is achieved through vertical pipes which are connected with the frame channel.
Boilers with horizontal boiler sections have several significant advantages over boilers with vertical boiler sections, especially the advantage, that the sections have to be interconnected only on one side of each section, so that the unavoidable dimensional changes during the operation and due to the heating can equalize without developing thermal stresses. Their disadvantage compared to the boilers with vertical boiler sections especially consists in the fact that the known horizontal boiler sections have a lower specific heat output -- in relation to the amount of material used -- than the vertical boiler sections and therefore require a larger specific amount of material used for the construction of the frame and the boiler section, increasing its weight and its cost.
The present invention has the object of providing a boiler with horizontal boiler sections which requires a substantially reduced specific amount of material used as compared with the known boilers of this type.
In accordance with the invention this object is achieved by providing a boiler with boiler sections consisting of a compact frame in which the pipes conducting the heat carrier medium are secured, wherein this frame is at least in heat conductive contact with the adjacent pipe or pipes by means of the fins provided on the pipe or pipes, and preferrably is connected with the pipe or pipes by means of an uninterrupted material to material contact.
Unexpectedly, it has been found, that the fins -- in the case of a connection to the frame elements -- besides taking up the heat from the flue gas and transferring it to the heat carrier medium contained in the associated pipe are also capable of conducting the heat taken up by the frame elements to the interior elements, so that in contrast to the formerly held assumptions a separate direct cooling of the frame by means of a heat carrier medium is not necessary. In this, generally a connection of the longitudinal frame members with the immediately adjacent heat carrier pipe is sufficient. However, it is also possible to provide a more extensive connection, wherein the convection fins form continuous cross bars. In this an arrangement is suitable in which the pipes carrying the heat carrier medium in boiler sections arranged on top of each other are also arranged on top of each other and their fins have a relative displacement. By means of this an optimum heat conduction is obtained -- by means of a suitable design in this also a turbulent flow of the flue gas can be obtained -- as well as a proper access from above to the surfaces in contact with the flue gas for cleaning purposes.
In a further alternative embodiment the fins of the individual boiler sections can be shaped so that they extend only as far as the splitting plane of the mold pattern. The fins of the other part of the pattern are then extending into the intermediate spaces. This embodiment has the advantage that all boiler sections are equal and thus only one mold pattern is needed for a design in which the heat carrier medium is supplied and discharged on one side in a common pipe for the whole boiler consisting of several boiler sections.
Furthermore, it is advantageous to provide "turbulators" in the form of deflector plates or vanes within the pipes at the levels of the heat conducting fins. On one hand these deflector plates increase the surface available for the heat transfer to the heat carrier medium and on the other hand create a turbulent flow in the heat carrier medium, thus preventing local overheating and therefore the occurence of boiling noises .